Java Interview Questions - Page 8
Question: What is the purpose of the finally clause of a try-catch-finally
statement?
Answer: The finally clause is used to provide the capability to execute
code no matter whether or not an exception is thrown or caught.
Question: What is the Locale class?
Answer: The Locale class is used to tailor program
output to the conventions of a particular geographic, political, or cultural
region.
Question: What must a class do to implement an interface?
Answer: It must provide all
of the methods in the interface and identify the interface in its implements
clause.
Question: What is an abstract method?
Answer: An abstract method is a method whose
implementation is deferred to a subclass. Or, a method that has no
implementation (an interface of a method).
Question: What is a static method?
Answer: A static method is a method that belongs to
the class rather than any object of the class and doesn't apply to an object
or even require that any objects of the class have been instantiated.
Question: What is a protected method?
Answer: A protected method is a method that can
be accessed by any method in its package and inherited by any subclass of
its class.
Question: What is the difference between a static and a non-static inner class?
Answer:
A non-static inner class may have object instances that are associated with
instances of the class's outer class. A static inner class does not have any
object instances.
Question: What is an object's lock and which object's have locks?
Answer: An object's
lock is a mechanism that is used by multiple threads to obtain synchronized
access to the object. A thread may execute a synchronized method of an
object only after it has acquired the object's lock. All objects and classes
have locks. A class's lock is acquired on the class's Class object.
Question: When can an object reference be cast to an interface reference?
Answer: An
object reference be cast to an interface reference when the object
implements the referenced interface.
Question: What is the difference between a Window and a Frame?
Answer: The Frame class
extends Window to define a main application window that can have a menu bar.
Question: What do heavy weight components mean?
Answer: Heavy weight components like
Abstract Window Toolkit (AWT), depend on the local windowing toolkit. For
example, java.awt.Button is a heavy weight component, when it is running on
the Java platform for Unix platform, it maps to a real Motif button. In this
relationship, the Motif button is called the peer to the java.awt.Button. If
you create two Buttons, two peers and hence two Motif Buttons are also
created. The Java platform communicates with the Motif Buttons using the
Java Native Interface. For each and every component added to the
application, there is an additional overhead tied to the local windowing
system, which is why these components are called heavy weight.